The antigenic components of canine and feline ovaries have not been investigated. It is of importance to characterize these components and identify any antigen that may be ovary-specific. Such antigens can be targets for raising ovarian antibody and, thus, provide an immunologic method to control fertility in the unwanted pet population. Results have indicated that there is at least one ovary-specific antigen in the canine, and the antibody raised against it would specifically bind with both ovarian homogenate and isolated canine ovarian cells.